这是来自 C 语言的思考。我看不到变量值是如何保留的

Question

此代码要求 3 个整数，确定奇数/偶数，添加偶数和偶数，赔率和赔率，这就是整个程序，除了我认为莫名其妙的行为之外，它与其他任何内容都没有共享，它的功能正是应该的。

scanf 显然是从 stdio 获取一个值，但它使用了 3 个不同的值，不会忘记它们并吐出正确答案，我不知道为什么，我很乐意牺牲我的前妻换一个回答。

/* lab3.c */
#include <stdio.h>

int main() {
    int osum = 0;
    int esum = 0;
    int n;

    scanf("%d", &n);
    if (n % 2 == 0)
        esum += n;
    else
        osum += n;

    scanf("%d", &n);
    if (n % 2 == 0)
        esum += n;
    else
        osum += n;

    scanf("%d", &n);
    if (n % 2 == 0)
        esum += n;
    else
        osum += n;

    printf("Sum of evens: %d\n", esum);
    printf("Sum of odds: %d\n", osum);
    return 0;
}

Answer 1

好的，让我们在每一行添加 cmets：

int main() {
  int osum = 0;  /* defines variable osum and initializes it to zero */
  int esum = 0;  /* defines variable esum and initializes it to zero */
  int n;         /* defines variable n */

  printf("Before starting, esum=%d, osum=%d\n", esum, osum);

  scanf("%d", &n);  /* reads an integer from stdin, assigns the value to n */
  if (n % 2 == 0)   /* if n is evenly divisible by 2.... */
    esum += n;      /* then n is added to esum, assigning the result to esum */
  else              /* otherwise n is not evenly divisible by 2... */
    osum += n;      /* so n is added to osum, assigning the result to osum */

  printf("After first read, esum=%d, osum=%d\n", esum, osum);

  scanf("%d", &n);  /* same as above */
  if (n % 2 == 0)   /*  "   "    "   */
    esum += n;      /*  "   "    "   */
  else              /*  "   "    "   */
    osum += n;      /*  "   "    "   */

  printf("After second read, esum=%d, osum=%d\n", esum, osum);

  scanf("%d", &n);  /*  "   "    "   */
  if (n % 2 == 0)   /*  "   "    "   */
    esum += n;      /*  "   "    "   */
  else              /*  "   "    "   */
    osum += n;      /*  "   "    "   */

  printf("Sum of evens: %d\n", esum);  /* prints esum */
  printf("Sum of odds: %d\n", osum);   /* prints osum */
  return 0;                            /* returns value of zero from main */
}

这是否有助于使其更清晰？

编辑

我采纳了@ElliotFrisch 的想法，并在每个 read-and-assign 部分之后添加了 printfs 以显示值如何变化。谢谢，艾略特！